Studies are being carried out on several aspects of cardiac metabolism and the effect of various drugs on nutrient use by the heart. Sugars, amino acids, and fats are being studied, and the effects of drugs which inhibit the use of sugars or fats by the heart, on the use of the other nutrients is being investigated. Drugs which alter the uptake of ions (salts) by the heart are also being studied, and the resistant effects on contraction and metabolism assessed.